Energizing and timing circuits for electromagnetic devices



May 23, 1950 c, s rr 2,508,973

ENERGIZING AND TIMING CIRCUITS 7 FOR ELECTROMAGNETIC DEVICES Original Filed April 10, 1943 TUBE 96 [L TUBE 84 TRANS.66/\

SOLENOlD TIME IN 300' no 2'0 a'o 40' 5'0 6'0 C.P.S.

AMPS.

TU BE LNO AMPS

TIMEIN 900 lo 20 so a 4 0 $0 a 60 r c.P.s. CLYDE E. SMITH Patented May 23, 1950 ENERGIZING AND TIMING CIRCUITS FOB ELECTROMAGNETIC DEVICES Clyde E. Smith, Warren, Ohio, aaaignor to The Taylor-Winfield Corporation, Warren, Ohio, a

corporation of Ohio Original application April 10, 1943, Serial No. 482,630. Divided and this application June 16, 1944, Serial No. 540,651

3 Claims. (Cl. 175-435) This invention, which is a division of the inventions disclosed in the copending application of Melvin M. A. Seelofl and Clyde E. Smith, Serial No. 482,630, filed April 10, 1943, now U. S. Patent No. 2,363,753, relates to energizing circuits for electromagnetic devices and to energizing circuits for such devices utilizing timing means to effect complete actuation of the electromagnetically operated devices in precisely timed relation with respect to the occurrence of an initiatingor reference condition.

More particularly, the invention relates to timed energizing circuits for solenoids which may be employed in the actuation of valves, for example, and the primary object of the invention is the provision of such electrical systems which will insure the completion of the actuating strokes of the armatures of the solenoids in an accurately timed and recurrently consistent mannor in response to the occurrence of initiating or reference electrical impulses or other reference conditions.

Another object of the invention is the provision of improved energizing circuits for electromagnetic devices whereby the design and construction of complete systems utilizing such devices may be materially simplified while their operation is dependable and uniform in successive cycles of operation. This general object is obtained, through employment of the principles of the invention, by delivering consistent waves of energy to the electromagnetic device in successive operations and by adjusting or controlling the nature of the wave so that movement of the armature of the device follows the pattern'required for optimum mode of operation of the complete system utilizing the device. Thus, in solenoid actuation of valves, for example, it may be desirable to insure the full opening of the valves in a predetermined number of milliseconds lrrespecive of the nature of the primary current source used 'in the operation thereof and in which the critical characteristics of the electronic tubes employed are not relied on for proper functioning thereof either in their ener- 1 gizing or timing aspects.

The above and other obiects and advantages of the invention will become apparent upon consideration of the following detailed specification and the accompanying drawing wherein:

Figure 1 is a schematic diagram of a timed energizing circuit for a solenoid having an operating armature, the circuit being constructed in accordance with the principles of the invention; and

Figures 2 and 3 are sets of characteristic curves illustrating the operation of the system of Figure 1, the sets representing characteristics under long and short periods of timing, respectively.

Referring to the drawing, L1 is an alternating current supply line leading from any suitable source while reference numeral 63 designates a solenoid which is to be energized by electrical energy derived initially from line L2. In accordance with the principles of the present invention, the solenoid 63 is arranged tobe energized by the discharge of a capacitor 61, this capacitor being shown as being connected to the solenoid through the conductors i8 and 69 in the latter of which is positioned a circuit controlling device preferably a thyratron 10. The value of capacitor 61 is chosen with regard to the total amount of energy required to effect the initial actuation of the solenoid armature and any element connected therewith and to maintain such armature and element in their actuated positions for a predetermined length of time. Having determined the value of capacitor 61 solenoid 63 is so designed that its operating circuit will have the following characteristics. First, the inductance of the coil when the armature is in retracted position is so chosen with respect to the value of capacitor 61 that an oscillatory circuit is effected in which the frequency is suchthat the current passes almost through the first one-half cycle thereof during the time that the armature moves to outer position. Thus positive and high speed operation is attained and the interval between the start of conduction in the device It and the full actuation of the armature and connected element is definitely predetermined. Secondly, solenoid 63 is so constructed that its inductance at the time the armature is in actuated position is sufliciently increased to shift the circuit constants beyond critical damping so that upon thev armature reaching its actuated position and its operated element being fully opened the current in the coil is unidirectional with a rate of decay low enough to hold the armature in outer position for the required or desired period of time. Upon the current decaying below a predetermined value the action of the plunger returning spring, not shown, returns the parts to their initial starting positions. Another important advantage of the presently described operating system is that the armature of the solenoid is first allowed to pick up speed before engaging the operating elements. Moreover, this desirable mode of operation is accomplished without variation in the time interval between the start of the flow of energizing current and the full actuation of th connected element or elements.

Capacitor 61 is arranged to be charged by a grid-controlled rectifier 1i deriving energy through a transformer 12 from an alternating current source-the line L2. Rectifier 1| is normally positively biased by a fixed voltage source 18 derivin energy from the line L2 through transformer 14'. This biasing circuit includes the positive end portion of a resistance 14 connected across the capacitor 61 and the biasing circuit may be traced from a cathode of rectifier 1| through the current limiting resistance 15, the positive end portion of resistance 14, adjustable tap 18 on resistance 14, conductor 11, resistance 13, conductor 18, and grid resistor 18 to the grid of the rectifier. As the charge on capacitor 61 approaches the value for which the tap 16 is adjusted the potential on tap 16 and conductor 11 will have become negative with respect to the cathode thus driving the grid negative in opposition to the potential of the source 13. The rectifler 1| will be extinguished but upon a drop of voltage across the capacitor 61 the rectifier will again conduct to maintain the selected charge on the capacitor. Connected in series across the capacitor 61 through the conductors 68, 8| and 88 is a variable resistance 82, a timing capacitor 83, and a thyratron 84. A resistance 85 having an adjustable tap 86 is in parallel with the series connected resistance 82 and capacitor 83 between the cathode of the thyratron 84 and the negative terminal of capacitor 61 through the conductor 88. Thyratron 84 is normally biased to cut-off by the potential developed across resistance 81 by a rectifier drawing energy from the line L2 through transformer 88. This biasing circuit may be traced from the cathode of thyratron 84 through resistance 85, a portion of conductor 88, conductor 88, resistance 81, conductor 88, the secondary of transformer 66, and conductor 8| to the grid of thyratron 84. While any suitable means, as a switch for example, may be employed to initiate operation of the timed energizing circuit, I have shown an impulse transformer 66 the primary of which is intended to be supplied with an impulse of current by the system with which the timed energizing circuit is associated. Transformer 66 is of the current type and connected across the secondary thereof is a resistor 82 across which a voltage is developed upon the flow of current in the transformer. This transformer is so phased that the polarity of its output as developed'across the resistor 82 is in opposition to the voltage developed across the resistance 81. Since the voltage across the resistor 82 is considerably greater than that of the fixed bias 81 the thyratron 84 will be rendered conductive immediately upon initiation of the fiow of welding current in the primary winding of transformer 66. Conduction in thyratron 84 places a major portion of the voltage across capacitor 61 across the resistance 85 and across the series connected timing capacitor 83 and potentiometer 82. Conv be energized under the control of the electronic valve 86 by the fiow of current through tube 84 and potentiometer 82 aided by the discharge of capacitor 83 whereby an impulse of steep wave front is impressed on the primary of the transformer. It will be observed that the anode of valve 86 is connected to the cathode of thyratron 84 as well as to the positive terminal of the capacitor 83 by means of the conductor 81 while the cathode thereof is connected through the primary of transformer 85 and conductor 88 to the negative terminal of capacitor 83 and also to the negative terminal of capacitor 61 through potentiometer 82 and conductor 88. Grid potential for valve 86 is derived from tap 86 of resistance 85. Before conduction in thyratron 84 capacitor 83 has no voltage appearing across it and therefore at the start of conduction the potential on conductor 88 and consequently on the cathode of valve 86 is more positive than the potential at the tap 86. Consequently the valve 86 will be held non-conducting until capacitor 83 is charged to a predetermined voltage at a rate determined by the setting of the potentiometer 82. Upon the capacitor 88 attaining a predetermined charge the potential on its cathode as derived through conductor 88 will become sufficientl negative with respect to the grid to start conduction in the valve 86. Current will then fiow through conductors 68 and 8|, thyratron 84, conductor 81, valve 86, primary of transformer 85, conductor 88, resistance 82, and through conductor 88 to the opposite side of capacitor 61. More important, however, is the discharge of capacitor 83 through conductor 81, valve 86, primary of transformer 85, and through conductor 88 to the negative terminal of capacitor 83. While the timing of the initiation of conduction in valve 86 is of critical importance for the proper and accurate functioning of the system, the relatively small total energy handled by this valve allows the use of a small tube having negligible temperature characteristics and a low impedance timing capacitor discharge circuit whereby any timing error resulting cathode connected to the negative terminal of capacitor 81 is a gas-filled discharge device I88, the grid of which is connected into the grid biasing circuit of the thyratron 18. Consequently tube I88 conducts when tube 18 conducts and causes the potential of slide 18 and of conductor 11 to drop down substantially to the potential of the negative terminal of capacitor 61. This 7| action drives the control grid of rectifier 11 high- 1y negative and the rectifier remains blocked until conduction ceases in tube 10 and 100. At a later time, depending on the time constant of the capacitor i! which is connected across conductor 18 and the cathode of rectifier 1|, rectifier 1i resumes conduction to charge capacitor 61 in preparation for the next succeeding cycle of operation. Since rectifier 11 is held non-conductive for a short interval even after the decrease of voltage across capacitor 61 to a value insuflicient to sustain conduction in thyratron the thyratron 84 and valve 96 are extinguished. It should be observed that the dead short characteristic of the discharge circuit for the capacitor 83 involving the valve 96 insures the complete discharge of the capacitor during each cycle of operation making it ready to accurately time the next succeeding operation.

The operating characteristics of the elements of the timing circuit are represented by the curves in Figures 2 and 3, the former dealing with a medium time setting while the latter is concerned with a very short timing period. The abscissae are laid off in time quantities represented by cycles having a frequency of 900 cycles per second after the period. It will be observed that in either case conduction in tube 84 is initiated within one to two milliseconds from the start of the voltage impulse from transformer 66 and that this delay is substantially constant. Upon the elapse of a predetermined interval as determined by the setting of the potentiometer 82 the tube 96 conducts and within one or two milliseconds the valve 10 begins to conduct to dump the energy stored in capacitor 61 into the coil 63. The sharp wave form of the current passed by tube 96 upon the timing out of the capacitor 83 should be particularly noted. This current passing through the primary of the transformer 95 results in a voltage wave in the secondary thereof of substantially identical form and it will be therefore understood that the time of firing of the tube 19 is substantially independent of the inherent characteristics of the tube. Thus extreme accuracy in timing is possible and the system illustrated has been proven to carry an accuracy of plus or minus 1.5% at normal timing intervals.

Figures 2 and 3 also show the correlation of operation of transformer 66 and-tubes 84 and 96 with the discharge of the capacitor 61, the curves of the latter being labeled solenoid. The peak values of the solenoid current curve represent the instants at which movement of the solenoid armature is completed and it will be observed that the time interval between the energization or start of conduction in tube 10 (initiation of discharge of capacitor 61 and the instant when the solenoid armature reaches its full actuated position is short and 'is substantially constant. This follows from the tuned nature of the solenoid energizing circuit as explained above.

It will be understood that any suitable means may be employed to charge the solenoid energizing capacitor and that insofar as the tuned nature of the energizing circuit is concerned other tripp means than that specifically disclosed may be employed to initiate discharge of the capacitor in timed sequence following the appearance of any desired reference condition.

Since the features of the invention disclosed herein are susceptible of widely varying embodiments the scope of the invention is not to be 6 limited except as necessitated by the prior state of the art and the scope of the appended claims.

What I claim is:

1. A timing and energizing circuit comprising in combination a capacitor, means to charge said capacitor, 9, gas discharge device having a control grid in control of the discharge of said capacitor a timing capacitor, means comprising a grid-controlled discharge device to charge said timing capacitor by energy derived from said first mentioned capacitor, and means operative upon said timing capacitor attaining a predetermined charge to discharge said timing capacitor through an impulsing device, said impulsing device being connected to said first mentioned control grid to initiate conduction in said gas discharge device.

2. A timing and energizing circuit comprising in combination a capacitor, means to charge said capacitor, means comprising a grid-controlled gas discharge device to discharge said capacitor a timing capacitor, an adjustable charging circuit for said timing capacitor including a circuit controlling device arranged to be rendered conductive upon the appearance of a reference condition, and means operative upon said timing capacitor attaining a predetermined charge to impress a voltage impulse on the grid of said gas discharge device to initiate discharge of said capacitor.

3. Electrical apparatus comprising an armature, an actuating coil therefor, a timed energizing circuit for said actuating coil comprising a capacitor, means comprising an impulse operated circuit controlling device to discharge said capacitor through said coil, a timing device, means to initiate operation of said timing device in response to the appearance of a reference condition, and means operative upon said timing device timing out its predetermined period to impress an impulse on said circuit controlling device to initiate discharge of said capacitor through said coil, the inductance of said coil being so related to the capacity and charge of said capacitor that said armature is moved from fully retracted position to fully actuated position during the rising portion of the current wave through said coil resulting from the discharge of said capacitor.

CLYDE E. SMITH.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,762,811 Charlton June 10, 1930 1,819,868 Carter Aug. 18, 1931 1,970,455 Humphries Aug. 14, 1934 2,024,019 7 Wright Dec. 10, 1935 2,040,677 Suits May 12, 1936 2,082,644 Lord June 1, 1937 2,127,080 Barker Aug. 16, 1938 2,249,488 Nickle July 15, 1941 2,296,580 Smiley Sept. 22, 1942 2,299,941 Townsend Oct. 27, 1942 2,356,765 Klemperer Aug. 29, 1944 FOREIGN PATENTS Number Country Date 318,316 Great Britain Sept. 5, 1929 551,058 Great Britain Feb. 5, 19 3 

